package com.captain.lc.lru;

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.Callable;

/**
 * Des:
 *
 * @author XL
 * @Date 2021/10/12 9:14
 */
public class LruByNaCos<K, V> implements Cache<K, V> {

    private final Cache<K, V> delegate;

    private Map<K, V> keyMap;

    private K eldestKey;

    public LruByNaCos(Cache<K, V> delegate, int size) {
        this.delegate = delegate;
        setSize(size);
    }

    @Override
    public int getSize() {
        return delegate.getSize();
    }

    public void setSize(final int size) {
        keyMap = new LinkedHashMap<K, V>(size, .75F, true) {
            private static final long serialVersionUID = 4267176411845948333L;

            @Override
            protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
                boolean tooBig = size() > size;
                if (tooBig) {
                    eldestKey = eldest.getKey();
                }
                return tooBig;
            }

        };
    }

    @Override
    public void put(K key, V val) {
        delegate.put(key, val);
        cycleKeyList(key);
    }

    @Override
    public V get(K key) {
        keyMap.get(key);
        return delegate.get(key);
    }

    @Override
    public V get(K key, Callable<? extends V> call) throws Exception {
        return this.delegate.get(key, call);
    }

    @Override
    public V remove(K key) {
        return delegate.remove(key);
    }

    @Override
    public void clear() {
        delegate.clear();
        keyMap.clear();
    }

    private void cycleKeyList(K key) {
        keyMap.put(key, null);
        if (eldestKey != null) {
            delegate.remove(eldestKey);
            eldestKey = null;
        }
    }
}
